This invention pertains to a machine for simultaneously placing cup-shaped stabilizing elements on the bottoms of plastic bottles intended to contain carbonated beverages, and pressure testing the bottles.
For reasons of tolerance to the internal pressures to which they are subject, such bottles usually have an approximately hemispheric bottom which is formed when the bottle is blow molded. The configuration of such a bottom does not allow the bottle to stand vertically unsupported on a planar surface. Moreover, this type of bottom is relatively more vulnerable to shocks than a bottom which is flat or which possesses a circular support collar.
To correct these disadvantages, these bottles are supplemented with mounted external stabilization and reinforcement elements, especially cups internally complementing the external profile of the base of the bottle and joined thereto by insertion and axial compression. On the outside the cup comprises a flat or annular base, of the type which conventional monolithic bottles have. A compound bottle is thus obtained, having both the characteristics required for the packaging of carbonated beverages and the stability advantages of any other bottle having a monolithic structure.
During the insertion of the cup on the hemispheric base of light bottles, it is important that the body of the bottles be stiffened so as not to deform under the effect of the axial pressures to which it is subjected. Without this precaution the bottle body would become deformed and would thus be rejected.
The most generally utilized method to stiffen the body of the bottle during the assembly of the cup with the bottle consists of pressurizing the inside of the bottle through the use of a gas, for example, aseptic air, which is injected through the neck of the bottle. When the assembly is completed the inside of the bottle is vented and the bottle is subsequently moved to an inspection station where it is again pressurized for a seal test. This process presents the inconvenience of requiring that the bottles be separately manipulated, pressurized and monitored for the seal testing operation, which increases the cost of the installations and decreases the production rates for the bottles.